Yesterday's thread on dungeon design led to some discussion of character rest in D&D. Specifically Carmedil didn't like that after an extended rest in 4E all characters were back at full health. I didn't perceive that as a specific problem, I've been playing since AD&D 1st edition and we ALWAYS rested until full health in every edition for the last 30 years. But more generally character rest poses a series of design questions:

How many battles are the characters "supposed to" do between rests?

How much weaker are characters in their second and subsequent battles compared to the first one of the day?

How much of their power / resources does a group recover by a rest?

How do you prevent groups from always resting after every fight ("5-minute workday" problem), and then always unloading all of their best abilities in that one fight per game day ("alpha strike")?

On the other hand, how do you prevent your group wiping because they stumbled into a major fight after already having exhausted most of their resources?

These questions aren't unique to D&D. Every pen & paper roleplaying system works with the players having some sort of resources, be that offensive like "spells" or "powers", or defensive like "hit points". An exciting battle is one which is well-balanced, and this balance can go out of the window if the players either have too many or too few resources at their disposal.

Apart from the game balance problem, there is also the problem of creating a logical and believable fantasy world. Going through a monster-filled dungeon with several battles in sequence is already a stretch, and more of a convention of the genre than something truly logical (Why doesn't the first monster ring an alarm and all monsters of the dungeon band together against the players?). The players sleeping for 8 hours after every 5-minutes of game time combat is throwing all logic out of the window.

In previous editions of D&D the 5-minute workday problem was a function of your character class. Character classes like fighters, who deal damage by using a weapon, consumed no offensive resources. As long as their defensive resources, hit points, were up, they could put out a constant stream of damage forever. Spell-casters on the other hand had a limited amount of offensive resources, X spells per day, with X being as low a 1 for a level 1 wizard. That meant that even after a successful and easy combat in which the group took no damage at all, the wizard might want to rest because he fired his only Magic Missile for the day, while the fighter didn't see any reason to rest.

4th edition D&D made huge improvements to this systems: First of all, ALL characters classes have the same number of daily powers. Second, ALL character classes have attacks they can use forever, as well as those daily powers, and powers they can use only once per encounter. Thus even if a group did alpha strike all their daily powers in fight one, they would still have a good selection of at-will and encounter powers in fight two without having to rest. Of course you still get conflicts between players who shoot their daily powers quickly and want to rest, and other players who tend to conserve their resources and want to carry on. But this now becomes a matter of player strategy, and not one of an inherent flaw in the rules system.

4E also made improvements to the defensive resources, by having both hit points and healing surges. Healing surges are a daily resource, so the answer to "when should the party rest?" becomes "when their healing surges are consumed". But as you can spend healing surges between fights in a short rest to heal yourself, you don't get into situations any more where the group stumbles into a fight while already being low on hit points. At worst you get into a fight while low on healing surges, and even most healing spells in combat only work if you have healing surges left.

After a long rest in 4E, characters regain all health, all healing surges, and all powers. That makes a long rest a true reset to the initial situation. Now I understand that some DMs (like Carmedil) would like a situation in which the group rests, but isn't at 100% after the rest. As a DM in 4E I can create this with special circumstances (e.g. resting in the Evil Temple of Doom results in players starting with less than full healing surges or powers). But if you make it a permanent rule that players don't regain health at night, you end up with a system which is very uneven, because how powerful the group is after a night's rest suddenly depends on how many healers they have. I *did* play a 1st edition AD&D cleric who on some adventuring days was forced to use all his spell slots for Cure Light Wounds, and had to use them right at the start of the day, leaving him no spell for the rest of the adventuring day. Not a fun system!

Still, any system can leave you with players wanting to rest after every fight. So what is a DM to do? There are some limited "carrots" he can offer: For example 4E has a system where after every 2 fights the group is said to have reached a milestone, and every milestone gives boni like an action point, or triggers magical item improvements like for an armor which gets better with each milestone. But mostly preventing constantly resting groups it is a matter of "sticks": Rests get interrupted by wandering monsters, for example. Or a part of the story is time-sensitive, where the group doesn't succeed in some goal if they don't reach it in a certain game time.

Ultimately every group has to find some sort of compromise with its DM. The DM just imposing his will is rather bad dungeon-mastering, and something that is ultimately doomed to fail because the players can always quit playing if they don't have fun. But most groups will be open to reason and accept that they can't just rest after every single fight. A bit of DM guidance, like "this place looks / doesn't look safe to rest", and the rest issue can be solved.